Method of making grain doors



March 27, 1956 H. T. MARTIN METHOD OF' MAKING GRAIN DOORS Filed Dec. l5. 1952 Jill gl@ K ifi; d

nited States Patent METHOD F. MAKING GRAIN DOORS ,Hollinshead T. Martin, Evanston, 'Ill., .assignor :to 'Signoile Steel strapping Company, Chicago, Ill., va corporation of Delaware Application December 15, 1952, SerialNo. 325,981

,2 Claims. (Cl. 154-118) This invention relates to Vgrain doors, that is, doors which are temporarily secured across the doorway opening of a carrier, such as a railway car, to retain therein, and to prevent leakage therefrom, loads of granular material.

The class of grain doors to which the invention pertains is exemplified by the patents to Herbert Corkran, N o. 2,116,260, dated May 3, 1938, and John M. Moon, No. 2,310,860, dated February 9, 1943. Such doors are 4intended for but a single use and are destroyed and thrown away when removed from the carrier. Consequently, it is of utmost importance that the cost of fabricating the grain doors be kept as low as possible while providing a door which may be quickly secured to the inside of the doorway frame of the carrier.

l Such doors are prefabricated and usually comprise two or more plies of impervious fabric material, which may be waterproofed, with cross or transverse metallic reinforcing straps between two of the plies. The plies of fabric and the straps are permanently bonded together by a suitable adhesive, and the doors are cut to widths slightly greater than the widths of the carriers doorway. Since these carriers are tted with conventional-usually sliding-doors at their outer faces, the `grain doors must be secured to the inner faces of the doorway frame to allow proper closing of the main car doors.

As grain land other spoilable granular material are customarily shipped in closed carriers-as, for example, box cars-the interiors of which are dark and unlighted, certain problems are encountered in nailing Athe grain doors to the doorway frame. It is not easy to drive the securing nails through the laminated paper ,reinforcing strap, and much waste of time and material accompanies nailing to the doorway frame a perfectly plain or imperforate grain door reinforced by imperforate strap. Furthermore, nails driven through the strap off the center and near the edges weaken the strap and even cause it to tear particularly when subject to a load. These difficulties can be overcome by perforating ythe strap, `but when the perforated strap is bonded between plies of imperforate fabric of suitable weight the perforations are covered and cannot be detected. Locating them also produces an undesirable waste of time yand material; also it has been found that the workmen ,installing the doors will not take the time to locate the hidden strap perforations. Various expedients have been suggested for indicating the location of the perforations, but none of them have proven entirely satisfactory. It is of course obvious that the strapping .and enclosing plies cannot be perforated through, even adjacent the sides of the doors, because these perforations would allow the granular material to leak through the grain door and defeat its purpose.

It is a principal object of the present invention to provide a new and improved grain door which affords an excellent indicia for locating the nail holes through .the metallic cross straps and which may be manufactured on conventiona-l laminating or combining machines.

Anotheriobject is -to provide a new and improved grain door `which overcomes the above described disadvantages substantially `coextensive.

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of the rprior doors :and which ymay be manufactured at less cost than the fprior art doors.

Another .object is `to provide -a :new and improved grain .door which can be economically vmanufactured in a number of heights and va'dfhs to fit known standard carrier 'doorway sizes.

And a further object is to provide a new and improved Prefabricated :grain door-way which may be manufactured at 'Iow cost so that the `door may be economically disycarded after a :single use.

Another object is to provide ya new and improved prefabricated grain vdoor which :may be manufactured from lwebs of imperforate fabric material and from imperforate strap which :during the manufacturing process are bondedA together, selectively perforated, and cut to suitable doorway widths.

lStill another ,object is ,to `provide a novel method of prefabricating the new and improved grain door of this invention.

Other :objects and advantages will become apparent from the following description vtaken in conjunction `with the accompanying drawing in which:

Fig. l is a perspective view of the grain door of the present invention installed in a lrailway car with portions ofthe inner and outer fabric plies broken away to illustrate `the construction of the door;

Fig. 2 is an enlarged fragmentary perspective view of one end ofthe grain door showing the manner in which ,the door -is nailed yto -the doorway frame; and

Fig. 3 is an )enlarged cross sectional detail vview taken along the line 3-3 of Fig. ,2, looking in the direction of the arrows.

The grain door of the present invention, indicated generally by :the reference character 1,0, is illustrated as installed in a ,railway car partially to close a doorway 12 defined inpart by a pair :of side .posts 14 and 16 to which the A,grain door 10 is nailed. The lgrain door bridges the doorway 12 to the desired load yheight .and overlaps the side Posts 1-4 and 16 to :which it is ynailed by an amount sufficient to insure :an adequate number-of nails through the door and into fthe Kpost to retain vthe door against the load within the car. In some installations it is preferred to protect the top fedge of `the door against damage by loading ,and unloading machinery by means of a head strip `nailed across the doorway .at the .top of the ygrain door. Also .in some .installations a foot strip is nailed across the ydoorway at the bottom -of the grain door.-

These vstrips have :been fomitted from .the illustrations for purposes of clarity, and their use is optional and well known in this art.

The grain 'door 10 consists of :two plies of fabric material, .an inner ply 1.8 and :an outer ply '20. lhese plies of fabric material -ma-y lbe made of a suitable relatively inexpensive material `such as paper. It will 'be observed from the drawing that vthe inner and outer plies are lf :the doors are made Ion a continuous combining machine the -width yof ythe plies is made the height of the grain door plus whatever may be needed for .an apron 22 xwhich is nailed to the flloor 24 of the railway car. The other dimension of vthe plies-that is in doorway width direction-,is such as to bridge the doorway and overlap .the side posts 14 .and 16 sufficiently to enable the grain door to be nailed thereto. Inasmuch as carriers, such :as railway cars, are produced with doorways .of known standard widths, the prefabrication .of these grain doors in standard sizes is readily extending metallic reinforcing straps 26.A These straps -are substantially as l'ong as the door panels are wide and are spaced suiciently to aiord the necessary load resisting qualities without undue expense and weight. Usually the spacing can be increased gradually from a region at or near the bottom of the door toward the top. In the door which is illustrated in the drawings and which from top to bottom measures six feet, the spacings of the reinforcing straps at the bottom are about four inches, and the spacings are increased to approximately six inches at the top of the door. and the door size are given merely by way of example and not limitation.V

For railway car grain doors, fabric plies of kraft calendered finish paper in thickness approximately .010, having a linear strength of about 130 pounds per inch of width and a cross-machine strength of about 50 to 55 pounds per inch, and reinforcing straps 26 of 3/1" by .020" cold rolled mild steel have been found in practice to give uniformly satisfactory results.

The inner and outer plies 1S and 20 and the spaced flexible metallic reinforcing straps26 interposed therebetween are made to cling to each other by bonding them together into a unitary whole with a thin layer of suitable adhesive 32 such as asphalt.

As seen most clearly in Fig. 3, the inner ply 18 and each of the metallic reinforcing straps 26 are provided with a series of perforations 2S adjacent the vertical edges of the grain door panel. These perforations extend through only the inner ply 18 and the straps 26 and do not extend through the outer fabric ply 20. Thus, the door as a whole is imperforate and no grain can leak or sift through it. The perforations 28 are located adjacent the edges of the door panel and extend inwardly therefrom in rows along the reinforcing straps 26, a typical row containing about ten perforations spaced about t" on centers. This arrangement of perforations 28 insures, when the door panel is held against the inside of a doorway frame, that at least a part of the perforations lie across the faces of the side posts 14 and 16. Since the perforations cut through the inner ply and the straps they are readily visible as the black asphalt ad` hesive contrasts sharply with the light color of the paper and of course the holes are easily found by the sense of touch. Because the perforations in the straps are uncovered the installing workmen can tension nail the grain door in place with nails 30-such as 8d. nails. In tension nailing the nails are introduced into the perforations 28 and used as prys to apply a slight tension to the straps to insure that the grain door 10 is properly stretched across the doorway opening 12. As both vedges of the door are provided with more perforations than actually necessary for an installation, each size of grain door 10 can accommodate small variations in the width of the doorway 12.

The door 10 is provided with a iiap or apron 22 which is folded upwardly along a score line 34. When the door is rolled for shipping the ap may be folded flat against the face of the inner ply 18. The apron 22 is reinforced by a metallic strap 36 and is provided with a series of spaced perforations (18 to 20 inches on centers) along its entire length, the perforations extending only through the inner ply 18 and the strap 36. When the door is installed in a carrier the apron 22 is laid` against the tioor, and nails 38, similar to the nails 30, driven through the perforations, secure the apron to the tloor thereby providing a seal against under the door leakage of the granular material being transported.

The grain door of this invention may be made by first bonding the straps 26 and 36 to one face, the inner face, of the inner ply 18 and then perforating the inner ply and the strapping by a suitable punch, such as a gang' punch. After the straps 26 and 36 and the inner ply 18 have been perforated as shown and described, the outer ply is then bonded to the inner ply and to the straps. The bonding of the outer ply 20 to the straps 26 and 36 and inner ply 18 which have been perforated These `spacings covers all the perforations at the outer face of the door but leaves the perforations 28 and those in the apron 22 on the inner face of thendoor exposed so that a workman installing the door in a railway car or other carrier can see the perforations by the contrast in color between the asphalt visible in the hole and the paper or can feel the nail holes with the nail point or his fingers, insert the nail through the nail hole and against the outer ply, stretch the door by using the nail as a pry, and then drive the nail until it is seated and holds the grain vdoor rmly against the doorway post or the car oor.

If the grain door is made on a machine which is continuous in its operation, then the plies of fabric 18 and 20 are fed in continuous webs and the imperforate strapping 26 is fed from rolls or coils of strapping between the plies. First the strapping 26 and 36 is bonded to the inner ply 18 by the asphalt adhesive and at predetermined spaced intervals approximately twenty holes are punched through the inner ply 18 and each of the straps 26, and the inner ply 18 and strap 36 are punched with a plurality of approximately equally spaced holes. Then the outer plyy 20 is bonded to the perforated inner ply 18 and strapping 26 and 36 and the traveling web of bonded plies and perforated strapping are cut transversely across the web to form the doors 10 of proper width, the transverse cut being through the center of the group of nail holesr28 so that each completed door is provided with a series of approximately ten holes through the inner ply 18 and strapping 26 adjacent its vertical edges.

From the foregoing description itV is clear that the grain door of this invention is inexpensive to manufacture and may readily be installed in a carrier such as a railway car and its installation made even though the car interior be quite dark. In `this specification the term grain door has been used as a matter of convenience in describing the door which is adapted to retain ali kinds of granular material, and no limitation of the invention or the .uses of the door'is intended.

While a preferred embodiment of the door constituting this invention has been shown andy described, it will be apparent that modifications and variations thereof may be made without departing from the underlying principles of the invention. It is, therefore, desired by the followingclaims to include within the scope ofthe invention all such variations and modifications by which substantially the result of this invention may be obtained through the use of substantially the same or equivalent means.

What is claimed as new and desired to be secured by United States Letters Patent is: s

1. The method of prefabricating load retaining doors which comprises bonding together a plurality of spaced metallic reinforcing straps and a first imperforate ply of fabric material, selectively perforating the metallic straps andthe first ply simultaneously, and bonding a second and imperforate ply to the perforated first ply and straps so as to enclose the straps between the plies.

2. The method of prefabricating load retaining doors which comprises continuously feeding a pair of webs of imperforate fabric material and a plurality of metallic reinforcing straps therebetween, bonding the straps to one of said webs, selectively perforating said one web and the reinforcing straps simultaneously, bonding the second web to said one web and the reinforcing straps so as to enclose the straps between the webs, and cutting the bonded fabric material and strapping into doorway` widths.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF PREFABRICATING LOAD RETAINING DOORS WHICH COMPRISES BONDING TOGETHER A PLURALITY OF SPACED METALLIC REINFORCING STRAPS, AND A FIRST IMPERFORATE PLY OF FABRIC MATERIAL, SELECTIVELY PERFORATING THE METALLIC STRAPS AND THE FIRST PLY SIMULTANEOUSLY, AND BONDING A SECOND AND IMPERFORATE PLY TO THE PERFORATED FIRST PLY AND STRAPS SO AS TO ENCLOSE THE STRAPS BETWEEN THE PLIES. 